Photographic emulsions containing symmetrical tetranuclear dyestuffs



Feb. 19, 1952 L. c. HENSLEY 2,586,164

PHOTOGRAFHIC EMULSIONS CONTAINING SYMMETRICAL TETRANUCLEAR DYESTUFFS Filed Oct. 51, 1950 INVENTOR Lee C. Hensley B LBW Patented Feb. 19, 1952 PHOTOGRAPHIC EMULSIONS CONTAIN- ING SYMMETRICAL TETRANUCLEAR DYESTUFFS Lee C. Hensley, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application October 31, 1950, Serial No. 193,285

. 4 Claims. 1 s

This invention relates to gelatino silver halide emulsions, "and particularly to photographic emulsions sensitized by means of new symmetrical tetranuclear dyestuffs in which the central nucleus, 4,4-bithiazole is linked to two-N-substituted rhodanine nuclei by a dimethine chain.

The use of sensitizing dyes, particularly in multilayer color film, poses many problems. It is known that sensitizing dyes operate bydyeing the silver halide grain. To do this, they must be adsorbed to the silver halide. If they are displaced from the silver halide grains, they lose their efiectiveness as sensitizers. It is also known that many color formers used in color photography have greater aifinity for silver halides than the sensitizers, and act to displace the same from the silver halide grains. One must, therefore, select a sensitizer which will not be so displaced.

Another-problem arises as regards the migration of the sensitizers from one emulsion to another. Where this ensues, color distortion is the inevitable result. Many proposals have been made dealing with the anchoring of compounds placement from silver halide grains by color formers, and (35 the ability to resist diffusion from one sensitized emulsion to another.

Efforts which satisfy the last prerequisite, unfortunately, often lead to compounds which will not meet the first two tests. Thus, it is known that thesensitizing power of cyanine dyes varies with the substituent on the cyanine N-atoms. Where this substituent is alkyl, the power decreases as the chain length increases. Hence, if a long alkyl chain be used to anchor the dye in the emulsion, we end-up with a product of little or no sensitizing power. The use of other expedients to anchor the dye, on the other hand, often gives products incapable of withstanding the displacement action of color formers insofar 2 as the silver halide grains are concerned. It is thus manifest that the provision of sensitizers having the necessary prerequisite is a dlfllcult problem, to say the least.

It is known that many cyanine dyes sensitize photographic silver halide emulsions to high red sensitivity. Most of these dyes, however, are not suitable for sensitizing silver halide emulsions containing color coupling components. This is thought to be due to a physical displacement which the sensitizing dye undergoes when color coupling components are added. That is, the sensitizer is adsorbed to the surface of the silver halide grain, and then, with addition of color coupling component, is displaced therefrom. An object of the present invention is to provide photographic gelatino silver halide emulsions with new symmetrical tetranuclear dyestuffs in which the central nucleus, 4,4'-bithiazole, is linked to two N-substituted rhodanine nuclei by a dimethine chain.

A further object is to provide such dyestuffs which are free from the disadvantages noted above. A

Other objects and advantages of this invention will become apparent by reference to the following specification in which its preferred details and embodiments are described.

This invention is predicted upon the discovery that symmetrical tetranuclear dyestuffs, in which the central nucleus, 4,4'-bithiazole, linked to two N-substituted rhodanine nuclei by a dimethine chain, are not only sensitizers for orthochromatic and panchromatic film emulsions, but are also compatible with color coupling components, being unaffected by the presence of color coupling components and exhibiting the property of non-.'- migration from the layer in which they are in-: corporated. In the latter combination, the sensitizing action of the dyestuffs is not impaired or diminished. An additional advantage of these dyestuffs is their ability to remain fixed in the layer in which they are originally deposited.

The symmetrical tetranuclear merocyanine dyestuffs fulfilling the above advantages are characterized by the following general formula:

wherein R represents an alkyl group, e. g., methyl, ethyl, propyl, butyl, etc., allyl and phenyl, and R1 represents an alkyl or aralkyl group, e. g., methyl, ethyl, propyl, isopropyl, butyl, etc., benzyl, phenethyl, and the like.

The process of preparing the above dyes comprises heating, preferably, under reflux conditions, with or without atertiary base, an alcoholic solution containing one mol of a di-quaternary cyclammonium salt of 2,2-dimethyl-4,4'-bithiazole and two mols of a rhodanine intermediate having a reactive acetanilido group linked to a monomethine chain adjacent to a keto group'of such intermediate. The rhodanineintermedi'ates are described in United States Patent No. 2,186,608.

As illustrative examples of such rho'danine intermediates, reference is made to:

-acetanilidomethylene-3-methylrhodanine S-acetanilidomethylene-3-ethylrhodanine 5-acetanilidomethylene-3-allylrhodanine 5Facetanilidomethylene-3 propylrhodanine 5-acetanilidomethylene 3 -phenylrhodanine 'Ifhe di-quaternary. cyclammonium salts of- 2,2- dimethyl-4,4-bithiazole utilized in the condensation' reaction are characterized by the following general formula:

S? S CH HC wherein R1 has-the same value as above and X represents anani'onic acid. radical, e. g., Cl, Br, I, C104, SO4CH3, SO4CiH5,- SOsCsHiCHs, and the product was 109-111 C. After crystallizing from petroleum ether (B. P. 60-75 0.), the melting point was 117 C. and the yield of the product was 13.6 grams.

One gram of 1,4-dibromobutane-2,3 and 0.63 gram of thioacetamide were dissolved in 20 cc. of absolute methanol and warmed for 10 minutes on the steam bath. The mixture. (2.. solid had separated) was poured'intolOOcc'. of'water. The aqueous mixture was made acid with diluted hydrochloric acid and filtered. Upon neutralization. a brownish solid appeared in the filtrate. This solid. was filtered off and recrystallized from methanol and had a melting point of 165 C.

The quaternization of the 2,2-dimethyl4,4'- bithiazole is eil'ectuated by fusion with an alkylatihg' agent; e. g'., an alkyl or aralkyl halide or by heating'thebase with an alkylating agent, e. g., an alkyloraralkylhalide in a sealed tube in a water bath under increased pressure in the usual manher. The alkylating agent employed may be methyl or ethyl iodide,.dimethyl sulfate, methyl p-toluen'esulfonate, phenethyl iodide, and the like.

As solvent-diluents employed in the preparation of the new dyes of the'present invention,- the following alcohols may be employed: methyl; ethyl; propyl, isopropyl, butyl, benzyl, furfuryl alcohol and the like. Triethylamine, tributylamine and the like are representative-of the tertiary bases which I may use.

The following examples describe in detail the methods of accomplishing the above objects, but it is to be understood that they are inserted merely for the purpose of illustration and are not to be construed as limiting the scopeoftheinvention.

Emample' I like. and are obtained by quaternizing 2,2'-dimetli'yl.-4',4"-bithiazole characterized by the following formula:

The"2,'2" -dimethyl=4,4'!-bithiazo1e is prepared in the following manner:

Eight: and six-tenths grams (0.1: mol) of but'anedione-ZB (diacetyD in 35. cc. of carbon disulfide were treatedxdropwisewith stirring; with asolutionof 101600. of 'bromin'e'in 20 cc. of carbon disulfide at the boiling point of the carbon disulfide. The addition was completedin 3 hours. The. stirring. andrheating were continued another 2 hours. After cooling, the; carbon disulfide was decanted irom the solid. which had separated. The crystals were washed with petroleum ether (P. B. (so-75 0.). The melting pointof the crude Example I was repeated with the exception 0 that 0.33 gram of 3-ethyl-5-acetanilidomethylenerhodanine was substituted for 0.35 gram of 3- allyl-5-acetanilidomethylenerhodanine. A tetranucle'ar merocyanine dyestuff was obtained which has approximately the same sensitizing properties as the dyestufl of Example I.

Example III Li s=d =0 \l Example I was repeated with the exception that 15 0.4 gram of S-phenyl-E-acetanilidomethylenerhodanine was substituted for 0.35 gram of 3- allyl-5-acetanilidomethylenerhodanine. The dyestufi obtained has approximately the same sensitizing characteristics as the dyestufi of Example I.

The diagrammatic spectrogram constituting the accompanying drawing illustrates the regions of the spectrum to which the symmetrical tetranuclear merocyanine dyestuffs will sensitize a gelatino silver halide emulsion containing 45% of silver halide and the extent of the sensitization at various Wavelengths. The single figure of the accompanying drawing illustrates the sensitizing properties of the dyes prepared in accordance with Examples I to III, respectively.

illustrations, or to the specific details given therein, but is capable of variations and modifications s s ESE O=CH CH= S \N/ \N/ 0= \N/ J=s wherein R represents a member selected from the class consisting of alkyl, allyl, and phenyl groups, and R1 represents a member selected from the class consisting of alkyl and aralkyl groups.

2. A photographic gelatino silver halide emulsion which contains a dyestuif of the following structure:

This application is a continuation-in-part of my application Serial No. 92,585, filed May 11, 1949, now abandoned, which was a division of application Serial No. 75,751, filed February 10,

3. A photographic gelatino silver halide emulsion which contains a dyestuff of the following structure:

1949, now abandoned. The sensitizing dyestufis. per se, are claimed in copending application Serial No. 189,487, filed October 10, 195-0, now Patent No. 2,553,503.

4. A photographic gelatino silver halide emulsion which contains a dyestufi of the following structure:

an. an.

While there have been pointed out above certain preferred embodiments of the invention, the same is not limited to the foregoing examples,

LEE C. HENSLEY.

No references cited. 

1. A PHOTOGRAPHIC GELATINO SILVER HALIDE EMULSION CONTAINING A SYMMETRICAL TETRANUCLEAR MEROCYANINE DYESTUFF CHARACTERIZED BY THE FOLLOWING GENERAL FORMULA: 